Folding chair

ABSTRACT

A folding chair which has a spring-resilient seat and a springresilient back, both of which are very thin- so thin that when the chair is folded, the lower surface of the seat lies within the chord across the back of the chair. Also, the spring resilience incorporates a two-way stretch action and other comfort structures.

United States Patent 1191 1111 3,845,984 Rowland 1 Nov. 5, 1974 FOLDINGCHAIR 2,794,492 6/1957 Hamilton et a1, 297/56 l' 4 1 1 Invent DawdRowland, 8 62nd S9 5,233,332 31133; $31121 3. 337133; New York, 100213,708,202 1/1973 Barecki et a1 297 335 x 22 Filed: Sept. 7, 1973 1 1 ppNOJ 395,365 Primary ExaminerBobby R. Gay

Related Application Data Assistant ExaminerlVilliam E. Lyddane [60]Continuation-impart of Ser, No, 268,870, July 3, Agent or firm-OwenWlckersham &

1972, which is a division of Ser. No. 126,808, March 22, 1971, Pat. No.3,720,568, Continuation-impart of Ser. No 268,907, July 3, 1972, whichis a division of Ser. No. 126,563, March 22, 1971.

[57] ABSTRACT [52] US. Cl. 297/56, 297/331 [51] Int. Cl. A47c 4/42 Afolding chair which has a spring-resilient seat and a [58] Field ofSearch 297/56, 57, 313, 331-335, spring-resilient back, both of whichare very thin-so 297/337, 338, 445, 452-458; 160/403, 404', thin thatwhen the chair is folded, the lower surface of 5/353, 354; 156/292;117/99; 161/57, 108, the seat lies within the chord across the back ofthe 112, 239; 267/ 107-1 11 chair. Also, the spring resilienceincorporates a twoway stretch action and other comfort structures. [56]References Cited UNITED STATES PATENTS 24 Chims, 19 Drawing Figures2,731,076 1/1956 Rowland 297/452 X PATENYEU W 5 I9 SEE 2 a :"IIIIIIII/ Am U FOLDING CHAIR CROSS-REFERENCE TO RELATED APPLICATIONS Thisapplication is a continuation-in-part of application Ser. No. 268,870,filed July 3, 1972, which was a division of application, Ser. No.126,808, filed Mar. 22, 1971, now US. Pat. No. 3,720,568.'

This application is also a continuation-in-part of application Ser. No.268,907, filed July 3, 1972, which was a division of application Ser.No. 126,563, filed Mar. 22, 1971.

BACKGROUND OF THE INVENTION This invention relates to a foldingchairhaving a spring-resilient seat and a spring-resilient back.

Folding chairs have long been knownTutankhamens tomb contained one.However, few of them have been comfortable, and compactness hasgenerally been confined to such as is gained merely by the act offolding in itself. The seats have generally been hard and whenupholstery was provided, compactness has been sacrificed. In fact,comfort has been achieved largely by padding, due to misunderstandingsabout the nature of comfort.

The seated human body rests 'mainly on the ischial tuberosities, the twolower points of the pelvis. Additionally, it rests on the meaty andfatty flesh in a l to 2 radius therefrom. The reason why a flat, hardsurface becomes uncomfortable quickly is that the load is concentr'atedon the small area of the ischial tuberosities, and the flesh immediatelycovering them is compressed with great force. Spreading this load over alarger area makes a more comfortable condition as the unit areacompressive force is substantially reduced. Automatically shaping theseat surface to generally conform to the sitter helps to accomplishthis. On the other hand, spreading this area over too wide a surface,such as is the case when a seat is too soft, results in engulfing thesitter too deeply and also often results in a lack of security, whichcomes from feeling insufficiently supported. One often sees automobilesin which the owner has gone to the trouble of installing wooden slataccessory pads to make the seat firmer.

Dr. Bengt Akerblom, eminent Swedish authority on human posture, says inhis book Standing And Sitting Posture, published by A. B. NordiskaBokhandeln, 1948:

Naturally a rather soft seat would distribute the pressure over thetuberosities better than a hollowed rigid one. They are, however, sosmall that there would be very little sense in having a very soft andresilient seat. On the contrary, such a seat might be expected totransfer a not inconsiderable proportion of the weight on to tissueswhich are not adapted for bearing it. The best consistency for the seatwould therefore be such that although it gave under pressure, it onlygave slightly.

Proper resilience alone is not enough, either. lndependent freedom ofmovement of such as that found in a two-way stretchable material moreappropriately conforms to the human posterior shape. which itself hascompound curvature.

While certain spring and padding combinations can afford properyieldability and firmness, practically all padding materials have thefault of being goodheat insulators. In a cold room, this might beacceptable temporarily, but people usually wear clothes appropriate fortemperature conditions anyway, and to sit for any length of time on aheat-insulative material becomes uncomfortable because of inhibition ofdispersion of body heat in the human posterior area. To get to a coolerspot, the person squirms. Also, anyone who, while wearing a swim suit,has tried to sit down on the seat of a convertible car that has been outin the hot sun, knows that such heat conditions of the seat can beunbearable.

Some prior art seats have been made of spaced-apart wires, but in themthe spacing has been such that too much load has been concentrated ontoo few wires, and this textural discomfort has made the use ofupholstery pads requisite for such seats.

An ideal seat therefore has:

1. Proper shape (including proper compound curvatures).

2. Proper resilience and firmness (resilience provides shapeadaptability to each sitter).

3. Proper heat dispersion.

4. Proper surface contact area.

One object of this invention is to provide a compactly folding chairwith a seat more nearly approaching the ideal than has been achieved inthe past.

Each seat or back of this invention comprises a series of sinuous springwires, partially held together by a thin sleevelike plastic coatingaround each of the wires, bridging the wires where they touch.

A disadvantage of some prior chairs was that the chair seat and backwere substantially planar, and, even if they did have a slight bowing,they were installed in a generally flat at-rest shape of the spring, sothat there was little spring tension or cushioning action. In thepresent invention, it becomes possible to obtain much more tension,cushioning, and resilient support from flat springs by virtue of makingthe unit as a cylindrical segment that is somewhat flattened when it isput on a chair frame, rather than making chairs from a series ofsubstantially flat springs. The tension of the wires pulling inwardly isone of the main forces retaining the assembly in place.

Another important feature of the invention is the provision of a two-waystretch, which is obtained by using plastic coatings lying within aprescribed range of Shoredurometers. The springs can continue theirflexing in the usual manner without being overly limited by thecoatings, and also the spring assembly can flex and stretch the plasticwhen it bridges the wires.

Even two-way stretchability and proper wire gauge alone have been foundto be insufficient. Resistance to bounciness is an important propertywhen considering the resilience necessary for a comfortable seat and isespecially necessary in transportation seating, where up-and-down motiontends to result in harmonic vibration, for harmonic vibrations subjectthe sitter to vertical oscillations for some time after a bump has beentraversed. Bounce dampening is thus requisite, and is partlyaccomplished in the presentinvention by proper choice of durometer ofthe plastic coating. 1f the durometer is too low a value, the springsare too free and are too ready to bounce. 1f the durometer is too high,the seat is too stiff and lacks the proper two-way stretch qualitydesired. Proper choice of durometer according to the principles of thisinvention, enables the plastic to serve as a shock absorber and providesa snubbing action against bounce.

Additionally bounce-dampening can be achieved in this invention byemploying in the assembly some wires that differ from the other wires ingauge, shape, or spring tension or temper, so that their harmonicvibration periods are different.

The amount of the seating area occupied by the metal thickness, and thethickness of the plastic coating are also important features to beconsidered, and little, if any, thought on these features is evidentfrom the prior art. I have found that for proper results the springsteel should occupy a minimum of 17 percent of the silhouette of thearea and, preferably, but less important, a maximum of about 75 percent,with the range of about l7 percent to about 25 percent generallypreferable. The coating should generally be about one-half as thick asthe wire, in order to give bridging, proper heat dissipation, and properstretchability, but a range from about one-fifth of the wire thicknessto about equal to the wire thickness can be used. Also, the size of thevoid areas between the coated wires should be no greater than about 75percent of the seat area used to accommodate one adult sitter and shouldnot be less than about 2 percent with about 60 percent to 75 percentbeing preferable.

SUMMARY OF THE INVENTION The present invention comprises a folding chairincorporating the sub-assembly set forth and claimed in my patentapplication Ser. Nos. 126,808 filed Mar. 22, 1971 and 268,907 filed July3, 1972. Basically, the subassembly is a cylindrical segment, laterflattened somewhat upon installation, placing the springs in tension.Sometimes it has a rim, which usually has straight ends, typicallyparallel, joined by parallel sides which are made as circular arcs;sometimes there is no rim. There is a series of sinuous spring wires,each of which is attached at its opposite ends to the rim, if there isone. The wires extend between their ends in a circular are which, whenthere is a rim, is parallel to the circular arc of the parallel sides ofthe rim. In most seats and backs each of the two extreme spring wires istangent at each cycle to one of the rim sides, and each wire touches orclosely approaches its adjacent sinuous spring wires at least once percycle.

A thin sleevelike plastic coating surrounds both the rim wires (if theyare present) and the sinuous spring wires, following the sinuous shapeof the spring wires and bridging between and joining them at pointswhere they are tangent to each other or touch each other, and alsojoining and bridging between the rim and some positions of the wires.This thin plastic coating, while leaving most of the area of the seatopen in between the wires, does link the wires and the rim together intoa unitary assembly, shaped as a cylindrical arc. When the unitaryassembly is installed on a frame as either a seat or a back, it isflattened out somewhat but not fully. When used as a seat, the risebetween one end and the other after flattening is between a quarter ofan inch and an inch, preferably. For the back, the curvature may besomewhat greater, preferably a radius of 7 to 20 inches. The plasticpreferably is in the range of Shore A durometers between 45 and 90, andseems to be best at about 75, so that the two-way stretch actionpreviously referred to is attained.

In some forms of the invention other shapes of rims are used, and instill other forms, no rim as such is necessary, being replaced by aspecial welded subassembly.

A folding chair of this invention has:

a. a first frame having at least two spaced-apart rigid frame portionsand two legs, b. a seat assembly having a series of arcuate, continuous,sinuous wires, each having two ends, each wire closely approaching eachof its immediately adjacent wires at frequent intervals, and

a thin sleevelike plastic coating surrounding the wires, following thesinuosity of the wires, and joining the wires together where theyclosely approach each other, the approaches being close enough foreffective bridging between them by the coating,

whereby the wires and plastic coating comprise a unitary assemblydefining a cylindrical are,

c. first mounting means for securing the seat assembly to the rigidframe portions of the first frame across a space that flattens the arcto a flatter arc and places the seat assembly in tension along theflatter cylindrical arc, which is convex upwardly,

d. a second frame having at least two spaced-apart rigid frame portionsand two legs,

e. a back assembly having the structure recited for element (b) above,

f. second mounting means for securing the back assembly to the rigidframe portions of the second frame across a space that flattens the arcto a flatter are which is convex rearwardly,

g. pivot means connecting the first and second frames together forenabling folding,

the seat, when the chair is folded, nesting within the back, with partof the lower surface of the seat lying within the chord across the back.

Note that in this invention the wires cannot go straight across. Theymust undulate in order to be stretchable. Moreover, they must beconnected to each other by stretchable means. This contrasts with anearlier patent of mine which may allow flexible joints but does notrequire stretchable joints. A l50-pound person sitting normally on achair of the present invention will depress it by at least 1 inch (or atleast oneeighteenth part of seat height) and, at most by about 3 inches(about one-sixth part of seat height). As stated, the junctures arestretchable and flexible, but they are also so tough that they cannot bepulled apart under usual human sitting conditions. Putty and kneadederasers have a rubbery quality, butnot the elasticity, stretchability,flexibility or resilience requisite. To get the best results in thisinvention, the area of the silhouette of the wires prior to coatingshould be at least 17% of the seat area, especially of a typical area.For sufficient bridging, heat dissipation, and surface cushioning, thecoating should be at least 20 percent of the wire diameter. If the seatwere made from springs alone, the comfort would be insufficient,particularly when used in moving vehicles. lt would be too bouncy.Proper durometer and proper thickness of the coating relative to thewire thickness help to prevent this bounciness. The reason is similar tothe reason why a car is not comfortable with metal springs along; italso needs the rubber, air, and hydraulic fluid in the combination ofrubberpneumatic tires and hydraulic shock absorbers, before it can becomfortable.

The folding chair of this invention has its seat convex upwardly'and itsback convex backwardly. Extraordinary compactness is achieved by havingthe seat fold into the back, such that the lower surface of the seatlies within the chord across the back of the chair.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a view in perspective of a folding chair embodying theprinciples of the invention.

FIG. 2 is a view in perspective on an enlarged scale of a seat or backunit or sub-assembly embodying the principles of the invention, shownbefore being installed on the chair frame of FIG. 1.

FIG. 3 is a view in section taken along the line 3-3 in FIG. 1.

FIG. 4 is a view in perspective of the fastener used in FIGS. 1 and 3 tosecure the sub-assembly of FIG. 2 to the chair frame in FIG. 1.

FIG. Sis a diagrammatic view in end elevation showing the difference inradii of the cylindrical assembly of FIG. 2 and the installed seat ofFIG. 1, which has been somewhat flattened out, thereby placing thespring wires under tension.

FIG. 6 is a fragmentary enlarged view in perspective of a corner portionof the assembly of FIG. 2, somewhat flattened out. Some portions arebroken away to show other portions that would otherwise be obscured.

FIG. 7 is a further enlarged view in section taken along the line 7-7 inFIG. 6.

FIG. 8 is a view in section taken along the line 8--8 in FIGS. 6 and 7.

FIG. 9 is a view in section taken along the line 9-9 in FIG. 7.

FIG. 10 is a view like FIG. 7 showing how the springs may be installedfrom the opposite direction in the same rim unit.

FIG. 11 is a view in front elevation of a modified form of folding chairembodying the principles of the invention. wherein the back frame isfixed to a riser as for use in a stadium or theater.

FIG. 11A is a front elevation of the seating unit of FIG. 11.

FIG. 12 is a view in side elevation of a seating unit of FIG. 11 in itsseat-down position.

FIG. 13 is a view like FIG. 12 with the seat folded up to rest in theback, a portion of the back being broken away to show the nesting.

FIG. 14 is a view in side elevation of the chair of FIG. 1.

FIG. 15 is a view in side elevation of the chair of FIGS. 1 and 14 inits folded position.

FIG. 16 is a diagrammatic view of the relative arcs and radii of theback and seat for the chairs of FIGS. 1 and 11-15, looking along theline C-C in FIGS. 13 and 15.

FIG. 17 is an enlarged top plan diagrammatic view in two halvesillustrating the two-way stretch effect of the wires and plasticassembly.

FIG. 18 is a fragmentary view in perspective of a portion of a modifiedform of seat assembly of the invention installed on a chair as the seatthereof and showing a corner near the rear of the seat. This viewillustrates the adaptability of the invention to double curvature in theseat, as occasioned by curvature of the supporting frame.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS An example of a folding chairembodying the invention (FIGS. 1, 14 and 15) Many. many types of foldingseating units may embody the principles of this invention, includingfolding chairs, folding sofas, folding davenports, stadium seating,theater seating, and so on.

A folding chair 20 is shown in FIG. 1 for the purpose of giving oneexample of a type of seating unit that can embody the principles of theinvention. This example is not to be construed as representing all typesof folding seating units or even all types of the folding chairs, whichcan vary greatly in frame structure, appearance. and so on. The basicpart of this invention is concerned with the seating and back unit morethan with the framework of the chair itself.

Embracing all these units within the term folding chair," the essentialfeatures are shown in FIGS. 1, l4 and 15, which show a folding chair 20.The chair 20 has a first frame 21 having at least two spaced-apart rigidframe portions or side frame portions 22 and 23 and two legs 24 and 25.The seat 26 itself is made from a seat assembly (FIG. 2) having a seriesof arcuate, continuous, sinuous wires 76, 76a, 76b 76n. Each wire hastwo ends 77 and 78, and each said wire 76, etc. closely approaching eachof its immediately adjacent said wires at frequent intervals. A thinsleevelike plastic coating 79 surrounds the wires 76, 76a, etc.,following the sinuosity of those wires and joining the wires togetherwhere they closely approach each other. The approaches are close enoughfor effective bridging between them by the coating 79. As a result, thewires 76, 76a etc., wires and the plastic coating 79 comprise a unitaryassembly 70 defining a cylindrical arc.

Suitable mounting means (See FIGS. 3, 4, 610, and 18) secure the seatassembly 70 to the side frame portions 22 and 23 of said first frame 21across a space that flattens the arc to a flatter are (See FIG. 5) andplaces the seat 26 in tension along the flatter cylindrical are, whichis convex upwardly.

A second frame 31 for the back has at least two spaced-apart rigid frameportions 32 and 33 and two legs 34 and 35. This second frame 31 supportsa back assembly 36, which also comprises an assembly 70A like thatconstituting the seat 26, but not necessarily identical in size, wiregauge, and so on. Again, suitable mounting means secure the backassembly 36 to the rigid frame portions 32 and 33 across a space thatflattens the arc to a flatter are, which is convex rearwardly.

Pivot means 40 and 40A connect the first and second frames 21 and 31together for enabling folding. An important feature is that when thechair 20 is folded, the seat 26 nests within the back 36, with the lowersurface of the seat 26 lying within the chord across said back. This isshown in FIG. 16.

The number of pieces used in making the chair frames is immaterial tothis invention, and whether the frames are continuous or are pieces. arewelded or otherwise secured together does not matter. so far as thepresent invention is concerned. The use of bracing and top members isnot significant in the present invention. though some such members areshown in the drawing,

and there must be some rigid means for holding the frame members 22 and23 apart and for holding the frame-members 32 and 33 apart. In thisparticular form of the invention the back frame members 32 and 33 arerigidly held parallel to each other and the side frame members 22 and 23are rigidly held parallel to each other. This parallelism need notalways be preset, but it is preferred.

The structure of the units 70 and 70A is highly important in thisinvention. 50 is the attachment of the units 70 and 70A to a chairframe. The units 70 and 70A may in some instances be identical, butusually the back unit 70A is somewhat smaller than the seat unit 70 andis usually made from a smaller gauge of wire. The Seat Unit 70 (P10. 2)

E16. 2 shows the seat unit 70 before it is incorporated into the chairs;the view also represents basically what the unit 70A looks like,although the unit 70A may be different in size or even in structure orappearance, where desired.

In this example, the unit 70 comprises a rim 71 having spaced-apartstraight ends 72 and 73 joined by parallel side members 74 and 75, whichare shaped as circular arcs. The member 74 which is to extend across thefront of the seat may be of thinner gauge than the wires 76, etc., inthe remainder of the seat. Lest there be some confusion in the mind ofthe reader, it is pointed out that the straight end members 72 and 73are secured to the side frame members 22 and 23 of the chair, and thusextend from front to rear at each side of the chair 20, while the sidemembers 74 and 75 become the front and back edges of the seat in theassembled chair 20. However, so far as the seat unit 70 itself isconcerned, the members 72 and 73 are the ends and the side members 74and 75 are arcuate or circular sides. As shown in FIG. 18, there need beno members 72 and 73.

Extending from end to end across the two end members 72 and 73 is aplurality of sinuous spring wires 76, 76a, 76b 76n, which are naturallyarched into a circular arc of the same size and shape as that of theside members 74 and 75. These springs 76, 760, etc., may have manyshapes, some of which are shown in the parent patent applications. Theymay be of the type often called non-sagging springs and sometimes soldunder the trademark No-Sag. Typical wires 76, etc., of this type are ofspring steel, having 0.60 to 0.75 percent carbon and 0.90 to 1.20percent manganese. Tensile strength typically runs about 215,000 to265,000 p.s.i., and their Rockwell hardness is about 39-41 RC range. Thediameter of the wires 76, etc., preferably lies in the range of 0.05 to0.15 inch. Too thick a wire tends to concentrate the stiffness too muchand the seat is too firm, while too thin a wire makes the seat too soft.Some of the wires may have different vibration frequencies than others,and some may be thicker than others, to snub vibration. Some wires maybe of different arc-cycle length than others, and some may be ofdifferent temper from others, to accomplish this purpose of snubbingvibrations.

Each end 77, 78 of each spring 76 (See FIGS. 6-10) may be firmlyanchored to and secured to one of the end members 72, 73 of the rim 71.Various means are employed to achieve this firm anchorage. and some ofthese are described below in following sections. They include frictiongrips and welding, among the many types of mechanical connections.

wires 76 and 76n being substantially tangent at each cycle to one of theside members 74 and 75. Each wire 76 touches its adjacent wires at leastonce per cycle. The touching may be actual contact or it may beapproximate touching or close approach, because, as will be seen, theassembly is held together in a way that does not require actual physicalcontact of the metal at each tangent point. but-it is always a veryclose relationship if not an actual touching.

A thin sleevelike plastic coating 79 surrounds the spring wires 76,follows their sinuous shape, and bridges the wires 76, 76a, etc., wherethey substantially touch each other. Preferably, the plastic coating 79is about one-half of the wire thickness, or in the range of aboutone-fifth of the wire thickness to about equal to the wire thickness. Atthe junctures, the thickness may be mostly greater, though the wiresthemselves may touch each other. This plastic coating 79 also surroundsthe rim 71 and links the wires 76 and the end and side members of therim 71 together into the unitary assembly 70. The plastic coating 79holds the wires 76 to each other as they span between the rim ends 72and 73, and it holds the side wires 74 and to the extreme springs 76 and76n at each point of tangency. The result is the arcuate or cylindricalarc shape, typically like that shown in FIG. 2, although the arc may besomewhat flatter or somewhat rounder.

Thus, the complete assembly 70 is a unit which can be sold or shipped asa unit'and can be assembled to the chair 20 of FIG. 1 or to many otherkinds of chairs, so long as the proper size and shape is accommodatedfor in one way or another, that is, either by the chair itself beingshaped to go with the seat unit 70 or the seat unit 70 itself made sothat it will go with a chair frame or other type of seating unit frame.The unit 70 by itself is capable of mass production, and is easilyassembled into a chair or other seating unit by securing the two endmembers 72 and 73 to a suitable rigid frame.

An lndependent Type of Securing Means (FIGS. 3 and Various securingmeans may be used, as described in the parent applications. Basically,the securing means may be an integral part of the unit 70, or may be anintegral part of the chair frame or other frame to which the unit 70 isto be secured, or it may be an independent member not an integral partof either of these. An example of the last-mentioned type is thesecuring member 80 shown in FIGS. 3 and 4. This may be a suitable metalor plastic member having a generally tubular rim-receiving portion .81,with an opening 82 therethrough that fits snugly around a rim member 72or 73. The member 80 has a pair of flanges 83,84 having an opening 85through them. As shown in FIG. 3, the chair frame member 22 may have aseries of openings 86 adapted to receive the two wings 83 and 84, afterthe member 80 has been fastened around the rim member 72 or 73. Then asuitable screw 87 may be inserted through a suitable opening 88 of theframe member 22 and secured by means of the openings 85 to the wings 83and 84. As shown in FIG. 1, there may be several of these units 80 tosecure the seat unit 70 and the back unit 70A to the chair 20.

From this it will be apparent that the assembly 70 and the assembly 70Amay be made as units by one manufacturer and sold to anothermanufacturer who makes the chair frames. So long as the dimensioning iscorrect, the two manufacturers need not know precisely what each otheris doing, for the unit 70, if made in the correct dimensions, can besecured to a variety of different types of chair frames, or to otherframes of seating members, for that matter, including benches,automobile frames, and so on. The unit 70 enables the chair manufacturerto secure the seat or back in place in the most attractive and pleasingand most practical way.

As will be seen from later portions of the specification, there aremany, many ways in which the fastening of the member 70 to the chair 20can be done, and this is just one example.

The Significance of Flattening the Cylindrical Arc (FIG.

FIG. 5 shows diagrammatically what happens when the unit 70 of FIG. 2 isput into the chair of FIG. I. The round cylindrical arc of FIG. 2 withradius R1 is flattened from the shape shown at the bottom of FIG. 5 tothe shape shown at the top of FIG. 5, where it has a larger radius R2.The unit 70 then has a broader span and its arc is somewhat flattened,so that it can be used as a seat. It has a crown height h, shown on thedrawing, and it is still a cylindrical are, though much flatter.

This flattening of a round assembly is an important feature of theinvention. By forming the unit 70 initially as a cylindrical arc, whichis quite round and fairly well closed, and then flattening itconsiderably, a large amount of desirable tension is placed into thecompleted unit 70, so that the seat has a springy feel to it, actingsubstantially as though there was a large cushion instead of simply anassembly of thin springs. The exact amount of crown height h or ofcurvature depends, of

.course, somewhat on taste, but generally there will be about a maximumof l-inch crown height h in a 16-inch wide seating unit 70, and theproportion is usually best considered as being a crown height h ofone-sixtyfourth to one-sixteenth of the span.

The amount of force required to flatten a seat of typical dining chairsize is important as well. For purposes of the present invention it hasbeen found that a collection of springs in an assembly 70, requiring aforce of between 340 pounds and 680 pounds to flatten it gives a seat ofproper tension (preferably around 500 pounds). This is the force exertedin pulling the two ends 72,73 apart to be of an appropriate distance tofit onto the chair frame members 22,23.

For the chair back, somewhat different rules apply and it will benoticed that in the chair of FIG. 1, as in most such chairs, the arc ofthe back extends rearwardly and is not something that the sitter tendsto flatten; rather, he tends to increase the arc curvature, reducing itsradius.

In both the seat and the back, the tension of the wires pullinginwardly, which results from flattening, is also one of the main forcesretaining the wires in place. Significance of the Plastic Coating 79(FIG. 17)

The plastic coating 79 may be chosen from various types of plastic, suchas polyvinyl chloride, polyvinyl acetate, mixtures thereof, other vinylcompounds, polyethylene, butadiene, acrylic elastomers, and so on. Thematerial may be transparent, where that is desired, or may be opaque andimpart its own color to the unit. It may contain dye or pigment whichimparts a desired color, completely preventing view of the wires 76themselves and giving the appearance of constituting the actual seatingmaterial. The plastic coating 79 may be semi-transparent and may giveshade or tone to the overall color.

It will be noticed that in this invention the plastic is confined to theunit or 70A and is not applied at all to the chair frame, so that thechair frame may have any surface or treatment that is desired withoutinterference from the nature of the plastic coating.

The sinuous wires 76 are preferably not welded to each other at theirpoints of tangency but are held together only by the plastic coating 79,with the wires 76 either touching each other or even slightly apart butclosely approaching each other. The same is true of the connectionbetween the wires 76 and the arcuate side members 74 and 75 of the rim71.

An important feature of the plastic coating 79 is that by choosing theproper range of durometer, a two-way stretch effect can be obtained, asillustrated in FIG. 17. The springs 76 not only stretch in thewell-known manner of non-sagging springs, but also the plastic coating79 between the adjacent springs 76 may be stretched, and this two-waystretch effect gives a wide range of resilience to the seat. If theplastic 79 is too hard, there can be substantially no such stretch, andif the plastic 79 is too soft, there will be too much stretch, thesprings 76 themselves are not properly availed of, and the unit 70 mighteven be tornapart after short use. By holding the Shore durometer of theplastic coating within critical values, the effect is right, withsufficient rigidity so that the springs 76 are taken advantage of and sothat they are held apart with sufficient resilience so that the whole isnot simply encased in a rigid covering. I have found that the durometerrange necessary to achieve this critical action is from about 45 toabout Shore A-scale durometer, with a preferable value of about 75.

In FIG. 17 there are two portions. The left portion illustrates part ofa seat 70 before it is sat upon, with the springs 76 therefore in theirnormal configuration. A typical area 280 is shown outlined, this areacomprising one complete cycle of wires 76, so that it is representativeof the total area of the seat 70 so far as the percentage of metalsilhouette per total area is concerned. This area can therefore be usedfor determining accurately the silhouette of the wire and its averageoccupation of the seat area. Taking the gauge or wire diameter as G, thelength of the wire can be determined in terms of G by measuring thelength of the center lines of all the wires 76 in the area 280 in termsof G, and the value is found to be 34G. The area 280 itself measures14.66 by l0.7G, which is l56.22G The silhouette area of the wire in thearea 280 is 340 which is 2 l .76 percent of the area 280. This valuelies within the required range of l7 percent to about 75 percent of theseat area, mentioned earlier, and also within the range of the preferredrange of 17 percent to about 25 percent.

Also, the empty spaces between the coated wires should be no greaterthan about 75 percent and no less than about 2 percent of the area ofthe seatsurface, and the range of about 60 percent to about 75 percentis preferred. The minimum of about 2 percent barely provides sufficientair ventilation.

The wires 76 in the seat 70 lie closely adjacent each other and nearlytouch at points of near-tangency, where the distance D1 between them, asshown in FIG. 39, may be as low as zero, and where the overall distancefrom the outside to the outside is TI. The plastic coating 79 forms abridge fastening the wires 76 together at 281 and has a thickness t.

The right portion of FIG. 17 illustrates what happens when the seat 70is stretched, as when it is sat upon. The length L1 in the left portionextends to the longer length L2 in the right portion. The width W1 inthe left portion extends also to become the width W2 in the rightportion. The distance D1 in the left portion has stretched to become thedistance D2 in the right portion, and the distance T1 has stretched tobecome the distance T2. Thus is seen the importance of the bridge orjuncture 281 and of the stretchability of the plastic 79 at this bridgeor juncture 281. This, of course, is related also to the thickness t ofthe plastic coating 79.

A glance at the seat 70 might lead one to conclude that the surfaceconfiguration would be texturally uncomfortable. However, thisconclusion would be mistaken, for the seat 70 acts differently than onemight at first conclude, for the following reasons:

I. The average occupation by the wire of the typical area (i.e., l7 to75 percent) is so great that the human posterior is supported withoutconcentrating the load too much. In contrast, if the wire occupies lessthan about 17 percent of the area (e. g., the 14.4 percent occupation ofthe FIG. 2 area in U.S. Pat. No. 2,803,293), the seat would betexturally uncomfortable.

2. The empty spaces constitute at least 2 percent of the seat area, inorder to give sufficient air ventilation, and preferably occupy muchmore of the seat area, up to about 75 percent.

3. The wire 76 is not exposed bare metal, which would be highly heatconductive and therefore unpleasant and uncomfortable. The wire 76 isadequately coated with plastic 79 which is low in heat conductivity; soit is pleasant and comfortable to sit upon.

4. The coating 79 lies within the range of Shore A durometers (45-90)where it is neither too hard nor too soft; in fact it tends in itself toprovide some cushioning effect, and its action at the bridges 281 addsto the comfort. Without this, the seat 70 could be too hard or too soft.

5. The two-way stretch discussed above provides automatic contouring,offering minimal resistance to the human posterior. Without this two-waystretch, the seat 70 might become increasingly uncomfortable.

Friction Fastening of the Wires to the Rim (FIGS. 640) While many meansof fastening the spring 76 to the rim 71 may be employed, some arenaturally preferred above others. The preference depends on manyfactors, such as manufacturers capabilities and preferments,specifications given by customers, and various features of cost andcapital equipment required.

One desirable type of fastening employs a friction lock principle, shownin FIGS. 6 to 10. In this form, the rim 71 has end members 72 and 73that are generally tubular; they may be made as a solid tube, but,preferably, as shown in the drawings, each member 72 or 73 is an opentube that may be made by curling a narrow strip of metal in a generallycircular shape. As shown, the member 72 or 73 has a flat bottom portion90 which is punched through at intervals to provide openings 91 andwings 92 and 93, extending at an angle such as about 30. Machines formaking these on either a batch basis or on a substantially continuousbasis are readily devised, so that the members 72 and 73 may be made aslong strips cut into desired lengths.

As will be seen by comparing FIGS. 7 and 10, the member 73 may beconsidered as being the same as the member 72, so that they arereversible; in other words, the same piece may be used in eitherdirection and at either end of the rim. Of course, bending in onedirection in reversal is a possibility, but no such reversal or sense ofdirection is required when the wings 92 and 93 are made as shown.

A series of side openings or slots 94 provide an entryway for the wireend 77 or 78. The wire end 77 or 78 is inserted in the opening 94 andthen moved lengthwise of the member 72 or 73 until it is stopped byengaging one of the wings 92 or 93. When inserted, the wire 76 depressesthe wing 92 (or 93) under pressure, but when it engages the end of thefar wing 93 (or 92), it can progress no farther. Thus, accuratepositioning is assured, and this can be made to provide automaticallythe desired tangencies of the wires 76 with each other and within theside members 74 and 75 of the rim 71. Once inserted, the wire end 77 or78 cannot be retracted, because on retraction, the depressed wing 92 (or93) digs into the wire 76 and prevents outward movement. The intentionis to prevent any relative movement between the wire end 77 or 78 andthe member 72 or 73 after assembly. The wire 76 can move across adepressed wing 92 in the direction toward a stop wing 93 but cannot moveback against the wing 92, once it hasbeen moved in. As shown in FIGS. 7and 10, the movement can be in either direction with the same effectexactly; it may be, of course, in opposite directions at opposite endsof the rim 71. Thus, the wires 76 are locked into the complete assemblyby friction in this form of the invention. The plastic coating 79 isapplied after this assembly is completed. Friction Fastening of theWires to the Rim (FIG. 18)

In FIG. 18 a frame member 41 is provided with a securing member 42 whichis a cylindrical segment, as seen in cross section, and has a main bodyportion 43 that may be welded to the frame member 41, a similar onebeing welded to the opposite frame member, not shown here. A series ofprojecting tongues 44 is provided; they may be initially bent up andthen bent down into place as shown in FIG. 5, after the wire ends 78have been approximately positioned so as to lock the wire ends 78 intoplace firmly by the members 44, clamping them between the members 44 andthe frame 41. As shown in FIG. 18, this may extend along a curve, but astraight line is equally possible in the present invention; this is avery important and unique effect of the present invention. It will beseen that with the members 42 welded on the frame members 41,installation is a relatively simple matter, involving principallyflattening out and stretching the arc of the subassembly 70, anchoringone end of it first and then anchoring the other end. The plastic 79 maycover the ends 77 and 78 or may not. but installation is the same inthis instance in both forms. Preferably a plastic bearing block liesbelow each tongue 44, preferably being made from plastic that is stifferin consistency than the coating 79, and it serves as a cushionpreventing the tongues 44 from abrading or cutting through the coating79.

The Folding Chair of FIGS. 1, 14 and 15 considered further FIGS. 14 and16 show a significant feature of the invention. The seat 26 is crownedupwardly and the back 36 is crowned rearwardly, so that when the chair20 is folded, the seat 26 can nest within the back 36 as shown in FIGS.and 16. This enables very compact folding of the chair 20, so that thethickness of the chair 20, in a stack of such folding chairs need be nogreater than the frame thickness.

Some of the features of the folding chair part are illustrated also inthe diagrammatic view of FIG. 16. This shows that the seat 26 may becurved less than the back 36, and in most examples this provides a morecomfortable chair than if they were curved only to fit each other. Theback concavity should be equal to or greater than that of the seat; inother words the radius of curvature of the seat 26 is greater than theradius of curvature of the back 36. The back 36 may vary from having aradius identical to that of the seat 26, to a radius no less than halfof the radius of the seat 26, in order to secure both comfort andadequate folding. Of course, when the curvatures are different, thestacking may be somewhat less compact, but this is a disadvantage to beweighed against the other disadvantage of having the seat and back beuncomfortable when sat upon.

in FIG. 16 is illustrated another unique feature of the invention. Theseat member 26 has a crown height of between A and l inch. When the seat26 is folded into the back 36, its under side 27 as well as its uppersurface 28 fits within the chord 37 of the back 36. Preferably, the back36 should have a radius of curvature R3 less than the radius ofcurvature R4 of the seat crown 26. The preferred radius R3 is between lland inches, and preferred R4 is 33 to 88 inches for 17- inch span.

A Stadium or Theater Seat (FIGS. l1-13) FlGS. 11-13 show a seatingassembly 100 having a back frame 101 which is secured to a riser 102that extends up between two floor levels 103 and 104. The back frame 101may be permanently welded or removably secured to a metal plate 105which may be secured to the riser 102 by bolts 106. Other structures maybe used to secure the back frame members 107 and 108 rigidly in place.Of course, the plate-and-riser structure may be replaced by another sortof frame supporting a whole series of chairs, like other theater chairsused on a sloping floor.

The seating assembly 100, one of many in a series, also includes a seatframe 110, which may comprise two rigid rods 111 and 112 each separatelypivoted to a back member 107 or 108 by a pivot pin 113 or 114. There maybe, but need not be, a rigid member between the rods III and 112.

The back frame 101 supports a back assembly 70A, and the seat framesupports a seat assembly 70 as before. and FIG. 16 applies to therelationship of the folded structures.

The thinness of the seats and backs of this invention are especiallyimportant. Thus, the thickness of the coated wire which is the seat orback thickness should be between one two-hundredths and onefifteenth ofthe cylindrical arc length of the assembly 70, i.e., of what is to bethe span of the seat or back.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein. are purely illustrative and are not intended to bein any sense limiting.

1 claim:

1. A folding seating apparatus, including in combination:

a. a first frame having at least two spaced-apart rigid frame portions,

b. a seat assembly having a'series of arcuate, continuous, sinuouswires. each having two ends, each said wire closely approaching each ofits immediately adjacent said wires at frequent intervals, and

a thin sleevelike plastic coating surrounding said wires, following thesinuosity of said wires and joining said wires together where theyclosely approach each other, said approaches being close enough foreffective bridging between them by said coating,

whereby said wires and plastic coating comprise a unitary assemblydefining a cylindrical arc,

c. first mounting means for securing said seat assembly to said rigidframe portions of said first frame across a space that flattens said areto a flatter arc and places said seat assembly in tension along theflatter cylindrical arc, which is convex upwardly,

d. a second frame having at least two spaced-apart rigid frame portions,

e. a back assembly having the structure recited for element (b) above,

f. second mounting means for securing said back assembly to said rigidframe portions of said second frame across a space that flattens saidare to a flatter are which is convex rearwardly, and

g. pivot means connecting said first and second frames together forenabling folding,

said seat assembly when said seating apparatus is folded nesting withinsaid back assembly, with part of the lower surface of said seat assemblylying within the chord across said back assembly.

2. The folding seating apparatus of claim 1 wherein each said assembly(b) and (e) includes a rim defining a closed area of a cylindricalsurface arched in one direction and straight in another direction normalto said arched direction, and having springy flexing action along saidarched direction,

said series of sinuous wires each being positively anchored at oppositeends to said rim and extending across said rim in a generally circularare parallel to the arching of said rim, the longitudinal axes of saidwires being parallel to each other, and

said thin sleevelike plastic coating surrounding said rim, linking saidwires to said rim in a unitary assembly shaped as a cylindrical arehaving a curvature of less radius than that desired in said seat orback.

3. The folding seating apparatus of claim 2 having means for mountingsaid rim on said frame members, and for flattening said wires somewhatto place the wires in tension along said flatter cylindrical arc.

4. The folding seating apparatus of claim 1 having mounting meansseparate from said coating for securing said assemblies (b) and (e) torespective fixed locations of their respective said rigid frame portions(a) and (d), thereby preventing relative sliding movement of said wirestherealong, said frame portions being so spaced apart that installationflattens said are to a flatter arc and places each assembly (b) and (e)in tension.

5. The folding seating apparatus of claim 4 wherein said mounting meanscomprises means for anchoring each of said wires adjacent their ends,the tension under which the wires are placed helping to retain them inplace.

6. The folding seating apparatus of claim 5 wherein each said mountingmeans engages the actual wire ends to prevent movement of the two endsof each said wire toward each other.

7. The folding seating apparatus of claim 4 wherein said wire ends liein the same arc as the remainder of their wire.

8. The folding seating apparatus of claim 7 wherein said mounting meanscomprises a member having transversely outwardly extending tongues towhich said wire ends are engaged, said tongues being bent down over saidwires.

9. The folding seating apparatus of claim 8 wherein said mounting meansis an integral portion of said frame, said tongues being bent outportions of said frame.

10. The folding seating apparatus fo claim 1 wherein said second frameis adapted to be secured to a riser on a rigid structure.

11. The folding seating apparatus of claim 10 wherein a plurality ofsaid second frames are attached to a single riser.

12. The folding seating apparatus of claim 1 wherein the seat crowns toa height above the ends of one sixtyfourths to one-sixteenth of the seatwidth.

13. The folding seating apparatus of claim 1 wherein said first frame iscurved and said seat is attached to the frame curve and is imparted acompound curvature.

14. The folding seating apparatus of claim 1 wherein the wires in theseat lying closest to the forward edge of the chair are of lighter gaugethan the wires of the seat in the central portion thereof, therebyimparting increased comfort.

15. The folding seating apparatus fo claim 1 wherein some of said wireshave a different vibration frequency from other wires, in order todampen bounce.

16. The folding seating apparatus of claim wherein some of the wires areof different thickness than others, to afford the bounce dampening tosaid assembly.

17. The folding seating apparatus of claim 15 wherein some of the wiresare of different configuration and arc-cycle length than others, toafford the bounce dampening.

18. The folding seating apparatus of claim 15 wherein some of the wiresare of different spring temper from others, to afford the bouncedampening.

19. The folding seating apparatus of claim 1 wherein said plasticcoating is stretchable.

20. A folding chair, including in combination:

a. a first frame having at least two spaced-apart rigid frame portionsand two legs, one attached to each of said frame portions,

b. a seat assembly having a series of arcuate, continuous, sinuouswires, each having two ends, each said wire closely approaching each ofits immediately adjacent said wires at frequent intervals, and

'a thin sleevelike stretchable plastic coating surrounding said wires,following the sinuosity of said wires and strechably joining said wirestogether where they closely approach each other, said approaches beingclose enough for effective bridging between them by said coating,

whereby said wires and plastic coating comprise a unitary assemblydefining a cylindrical arc.

c. first mounting means for securing said seat assembly to said rigidframe portions of said first frame across a space that flattens said areto a flatter arc and places said seat assembly in tension along theflatter cylindrical arc, which is convex upwardly,

d. a second frame having at least two spaced-apart rigid frame portionsand two legs, one attached to each of said frame portions,

e. a back assembly having the structure recited for element (b) above,

f. second mounting means for securing said back assembly to said rigidframe portions of said second frame across a space that flattens saidare to a flatter arc which is convex rearwardly, and

g. pivot means operatively connecting said first and second framestogether, the legs being operatively connected to their respectiveframes and to each other, thereby enabling folding of said chair,

said seat assembly, when said chair is folded, nesting within said backassembly, with part of the lower surface of said seat assembly lyingwithin the chord across said back assembly.

21. The folding chair of claim 20 wherein said coating constitutes thesole means holding the wires of said seat and back assemblies together.

22. The folding chair of claim 21 having mounting means separate fromsaid coating for securing each said assembly to respective fixedlocations on their respective said rigid frame portions and therebypreventing relative sliding movement of the wires along said frameportions, said frame portions being so spaced apart that installationflattens said are to a flatter arc and places the assembly (b) intension, whereby resilience for seating comfort is obtained both by thearcing and tensioning of said wires and by the stretchability of saidcoating where it bridges between said wires.

23. The folding chair of claim 20 wherein said assembly comprises a rimdefining a closed area of a cylindrical surface, arched in one directionand straight in another direction normal to said arched direction, andhaving springy flexing action along said arched direction,

said series of sinuous wires each being positively anchored at oppositeends of said rim and extending across said rim in a generally circularare parallel to the arching of said rim, the longitudinal axes of saidwires being parallel to each other, said thin sleevelike stretchableplastic coating surrounding said rim, stretchably linking said wires tosaid rim in a unitary assembly shaped as a cylindrical are having acurvature of less radius than that desired in said seat or back. 24. Thefolding chair of claim 23 having means for mounting said rim on saidframe members, and for flattening said wires somewhat to place the wiresin tension along said flatter cylindrical arc.

1. A folding seating apparatus, including in combination: a. a firstframe having at least two spaced-apart rigid frame portions, b. a seatassembly having a series of arcuate, continuous, sinuous wires, eachhaving two ends, each said wire closely approaching each of itsimmediately adjacent said wires at frequent intervals, and a thinsleevelike plastic coating surrounding said wires, following thesinuosity of said wires and joining said wires together where theyclosely approach each other, said approaches being close enough foreffective bridging between them by said coating, whereby said wires andplastic coating comprise a unitary assembly defining a cylindrical arc,c. first mounting means for securing said seat assembly to said rigidframe portions of said first frame across a space that flattens said arcto a flatter arc and places said seat assembly in tension along theflatter cylindrical arc, which is convex upwardly, d. a second framehaving at least two spaced-apart rigid frame portions, e. a backassembly having the structure recited for element (b) above, f. secondmounting means for securing said back assembly to said rigid frameportions of said second frame across a space that flattens said arc to aflatter arc which is convex rearwardly, and g. pivot means connectingsaid first and second frames together for enabling folding, said seatassembly when said seating apparatus is folded nesting within said backassembly, with part of the lower surface of said seat assembly lyingwithin the chord across said back assembly.
 2. The folding seatingapparatus of claim 1 wherein each said assembly (b) and (e) includes arim defining a closed area of a cylindrical surface arched in onedirection and straight in another direction normal to said archeddirection, and having springy flexing action along said archeddirection, said series of sinuous wires each being positively anchoredat opposite ends to said rim and extending across said rim in agenerally circular arc parallel to the arching of said rim, tHelongitudinal axes of said wires being parallel to each other, and saidthin sleevelike plastic coating surrounding said rim, linking said wiresto said rim in a unitary assembly shaped as a cylindrical arc having acurvature of less radius than that desired in said seat or back.
 3. Thefolding seating apparatus of claim 2 having means for mounting said rimon said frame members, and for flattening said wires somewhat to placethe wires in tension along said flatter cylindrical arc.
 4. The foldingseating apparatus of claim 1 having mounting means separate from saidcoating for securing said assemblies (b) and (e) to respective fixedlocations of their respective said rigid frame portions (a) and (d),thereby preventing relative sliding movement of said wires therealong,said frame portions being so spaced apart that installation flattenssaid arc to a flatter arc and places each assembly (b) and (e) intension.
 5. The folding seating apparatus of claim 4 wherein saidmounting means comprises means for anchoring each of said wires adjacenttheir ends, the tension under which the wires are placed helping toretain them in place.
 6. The folding seating apparatus of claim 5wherein each said mounting means engages the actual wire ends to preventmovement of the two ends of each said wire toward each other.
 7. Thefolding seating apparatus of claim 4 wherein said wire ends lie in thesame arc as the remainder of their wire.
 8. The folding seatingapparatus of claim 7 wherein said mounting means comprises a memberhaving transversely outwardly extending tongues to which said wire endsare engaged, said tongues being bent down over said wires.
 9. Thefolding seating apparatus of claim 8 wherein said mounting means is anintegral portion of said frame, said tongues being bent out portions ofsaid frame.
 10. The folding seating apparatus fo claim 1 wherein saidsecond frame is adapted to be secured to a riser on a rigid structure.11. The folding seating apparatus of claim 10 wherein a plurality ofsaid second frames are attached to a single riser.
 12. The foldingseating apparatus of claim 1 wherein the seat crowns to a height abovethe ends of one sixty-fourths to one-sixteenth of the seat width. 13.The folding seating apparatus of claim 1 wherein said first frame iscurved and said seat is attached to the frame curve and is imparted acompound curvature.
 14. The folding seating apparatus of claim 1 whereinthe wires in the seat lying closest to the forward edge of the chair areof lighter gauge than the wires of the seat in the central portionthereof, thereby imparting increased comfort.
 15. The folding seatingapparatus fo claim 1 wherein some of said wires have a differentvibration frequency from other wires, in order to dampen bounce.
 16. Thefolding seating apparatus of claim 15 wherein some of the wires are ofdifferent thickness than others, to afford the bounce dampening to saidassembly.
 17. The folding seating apparatus of claim 15 wherein some ofthe wires are of different configuration and arc-cycle length thanothers, to afford the bounce dampening.
 18. The folding seatingapparatus of claim 15 wherein some of the wires are of different springtemper from others, to afford the bounce dampening.
 19. The foldingseating apparatus of claim 1 wherein said plastic coating isstretchable.
 20. A folding chair, including in combination: a. a firstframe having at least two spaced-apart rigid frame portions and twolegs, one attached to each of said frame portions, b. a seat assemblyhaving a series of arcuate, continuous, sinuous wires, each having twoends, each said wire closely approaching each of its immediatelyadjacent said wires at frequent intervals, and a thin sleevelikestretchable plastic coating surrounding said wires, following thesinuosity of said wires and strechably joining said wires together wherethey closely approach each other, said approachEs being close enough foreffective bridging between them by said coating, whereby said wires andplastic coating comprise a unitary assembly defining a cylindrical arc,c. first mounting means for securing said seat assembly to said rigidframe portions of said first frame across a space that flattens said arcto a flatter arc and places said seat assembly in tension along theflatter cylindrical arc, which is convex upwardly, d. a second framehaving at least two spaced-apart rigid frame portions and two legs, oneattached to each of said frame portions, e. a back assembly having thestructure recited for element (b) above, f. second mounting means forsecuring said back assembly to said rigid frame portions of said secondframe across a space that flattens said arc to a flatter arc which isconvex rearwardly, and g. pivot means operatively connecting said firstand second frames together, the legs being operatively connected totheir respective frames and to each other, thereby enabling folding ofsaid chair, said seat assembly, when said chair is folded, nestingwithin said back assembly, with part of the lower surface of said seatassembly lying within the chord across said back assembly.
 21. Thefolding chair of claim 20 wherein said coating constitutes the solemeans holding the wires of said seat and back assemblies together. 22.The folding chair of claim 21 having mounting means separate from saidcoating for securing each said assembly to respective fixed locations ontheir respective said rigid frame portions and thereby preventingrelative sliding movement of the wires along said frame portions, saidframe portions being so spaced apart that installation flattens said arcto a flatter arc and places the assembly (b) in tension, wherebyresilience for seating comfort is obtained both by the arcing andtensioning of said wires and by the stretchability of said coating whereit bridges between said wires.
 23. The folding chair of claim 20 whereinsaid assembly comprises a rim defining a closed area of a cylindricalsurface, arched in one direction and straight in another directionnormal to said arched direction, and having springy flexing action alongsaid arched direction, said series of sinuous wires each beingpositively anchored at opposite ends of said rim and extending acrosssaid rim in a generally circular arc parallel to the arching of saidrim, the longitudinal axes of said wires being parallel to each other,said thin sleevelike stretchable plastic coating surrounding said rim,stretchably linking said wires to said rim in a unitary assembly shapedas a cylindrical arc having a curvature of less radius than that desiredin said seat or back.
 24. The folding chair of claim 23 having means formounting said rim on said frame members, and for flattening said wiressomewhat to place the wires in tension along said flatter cylindricalarc.